Wall ball



FIG. 1 is a front view of the wall ball showing our new design;

FIG. 2 is a right side view thereof, the left side view being identical thereto;

FIG. 3 is a bottom view thereof; and,

FIG. 4 is a top view thereof.

The broken lines are included for the purpose of illustrating portions of the wall ball that form no part of the claimed design. 

The ornamental design for a wall ball, as shown and described. 